Molding flask for dental impressions



Dec. 22, 1964 L. WILAND MOLDING FLASK FOR DENTAL IMPRESSIONS Filed April 12, 1963 I NVEN TOR. LA E/vac- MLH/YD United States Patent Ofi flce ddfllfil'l Patented Dec. 22, 1964 3,161,917 MGLDEVG FLASK FGR DENTAL HviPRESSlONS Lawrence Wiland, 42-45 Kissena Blvd, Flushing, NY. Filed Apr. 12, 1963, Ser. No. 272,785 Claims. (Ci. l834.l)

This invention relates to molding flasks for forming dental castings from dental impressions.

It is an object of my invention to provide a molding flask which will yield highly accurate dental castings from dental impressions and which will prevent distortion of the dental impression during the casting process.

It is another object of my invention to provide a molding flask of the character described which Will allow usage of a minimum quantity of casting material to mold the dental casting and which will thereby form a casting requiring little or no removal or trimming of surplus casting material.

It is a further object of my invention to provide a molding flask of the character described which is especially adapted for use with a standard impression tray and which will snugly seat such tray during the casting process so that a dental casting is formed which is uniformly dense without internal faults and which is an exact replica of a patients tooth and gum structure.

It is a further object of my invention to provide a. molding flask of the character described which is unitary in structure and does not requi e the coupling or addition of further parts to complete the flask, so that the dental impression may be cast immediately after it has been formed in and removed from the patients mouth. Such characteristic prevents creep or distortion of the impression material prior to molding and conserves the time of the dentist or the dental technician.

It is another object of my invention to provide a molding flask of the character described which is simple and economical in manufacture and which is well suited for the conditions of practical use by a dentist in his ofllce or by a dental technician in a dental laboratory.

In general, I achieve the above objects and effectuate my invention by providing a one-piece cup-shaped flexible resilient molding flask, i.e. a flask comprising a bottom wall and a continuous upstanding side wall unitarily joined to and encircling the bottom Wall. The molding flask has its interior surface complementally shaped to seat a standard dental impression tray which carries the impression of a patients mouth in an elastic impression medium. Due to the flexible and resilient nature of the material forming the flask and to the complemental shaping of the flask to the tray, the tray is quickly and easily seated in the flask and the flask effectively seals itself around the border or" the tray so that the casting material will not intrude into the region around said border where it subsequently will harden and require trimming.

Preparatory to the molding of the casting, the impression tray is seated within the flask so that the tray with its impression material in effect constitutes a new bottom wall for the molding flask, the tray being oriented with its impression material upwards.

With the impression tray thus in place, a molding cavity is formed which, when cast, will yield a highly accurate replica of the patients tooth and gum surfaces. The bottom wall and a unitary internal shoulder on the upstanding side wall snugly fit to the tray and as observed above will by virtue of the flexible and resilient character of the flask prevent casting material from running around and underneath the impression tray and from forming a cast ing containing large surpluses of cast material which later must be removed. The mentioned internal shoulder also aids in preserving an accurate impression of the mucobuccal fold of the patients mouth.

Other objects of my invention in part will be obvious and in part will be pointed out hereinafter.

My invention accordingly consists in the features of construction, combinations of elements and arrangements of parts which will be exemplified in the device hereinafter described and of which the scope of application will be indicated in the appended claims.

In the accompanying drawings in which are shown one of the various possible embodiments of my invention,

FIG. 1 is a perspective view of a molding flask embodyin my invention and an impression tray carrying impression material thereon preparatory for insertion into the flask;

FIG. 2 is a vertical cross-sectional view of the molding flask with the impression bearing tray inserted therein, said view being taken substantially along the line 22 of FIG. 1;

FIG. 3 is a vertical cross-sectional View taken substantially along the line 33 of FIG. 2;

FIG. 4 is a view similar to FIG. 2 but with molding material in the molding cavity of the molding flask; and

FIG. 5 is a perspective view of a dental casting formed by the molding flask.

Referring now in detail to the drawings, the reference numeral 1% denotes a molding flask embodying my invention. Said molding flask is used with an impression tray 12 carrying impression material id.

The impression tray 12 is of standard manufacture and such trays are sold in various sizes to accommodate variations in the dimensions of the arch of the dental patients mouth. Further, these trays are divided into two types, one for the upper tooth formation and one for the lower tooth formation. Although only one size and type of impression tray has been shown, a reader of the instant disclosure skilled in the art will understand that molding flasks of different sizes and types are provided to be used with different sizes and types of trays.

Such impression tray 12 includes a body portion 16 and a handle 13 joined to the body portion and extending rearwardly therefrom parallel to the general horizontal plane of the body portion.

The body portion 16 is in the shape of a scoop or shovel and has an interior impression-materialbearing trough 17 which corresponds generally to but is somewhat larger than the outline of the tooth and gum surfaces of the patients mouth.

The body portion 16 includes a rear semicircular upstanding retaining side wall or border Zil which converges to meet a flat horizontal front edge 21 of a bottom wall 22. The upstanding wall it) acts as the outer and rear bearing surface of the body portion 16 to hold the impression material 14 in place on the bottom wall 22 of the impression tray, i.e. in the impression material trough 17. Said border 2t? has a speciiic elevational contour (best shown in H6. 1) which, as is conventional, is selected to provide the desired exposure of the impression material to the tooth, gum, and buccal surfaces. Customarily said contour provides a low height at the front side of the border which rises first steeply and then gradually to near the rear center of the border where the contour dips to form a cusp Ella therein. The bottom Wall 22 of the impression tray 12, which the upstanding border 20 partially encircles (except at the front of the tray), includes a convex central hump which generally conforms to the palate area of the mouth. In accordance with standard dental practice, a suitable elastic-type impression material such as a hydrocolloid, alginate, rubber-base material or silicon-base material is placed on the impression tray 12. The tray, with the impression material 14 thereon, is placed in the patients mouth in position against the gum, teeth and check structure. The tray will be placed against either the upper or lower structure depending on the type of tray used so as to give a complete reproduction of the mouth shape and tooth contour, as shown in FIG. 1. An upper tray is illustrated. A lower tray difrers most noticeably in that its trough (corresponding to the trough 17) is fully U-shaped in vertical cross-section and is U-shaped in plan. 7

The flexible flask it is made from a self-form-maintaining flexible and resilient material, e.g. a dead soft rubber or polyvinylchlori-de and comprises a flat base 24 and a continuous upstanding wall 26 joined to and integral with the base 24 around the entire periphery thereof. The molding flask material preferably has a Durometer reading of 15 to 18. The wall 26 has a rear semicircular portion and a front straight portion, the interior surfaces of said portions being congruent to but larger than the irregular circumference of the tray 12. The wall 26 has an interior height which extends higher than the tray 12 when the tray is seated within the flask. The upstanding wall 26 includes a horizontal open ended through slot 27 located at the junctureof the wall 26 and the base 24 at the rear of the flask and passing from the exterior to the interior of the flask 10. The width and height of the slot 27 match generally like dimensions of the tray handle '18 and said slot is positioned to pass said handle when the tray is seated in the flask.

The interior surface of the base 24 of the flask for the upper tray includes a central hump 28 having a generally U-shaped peripheral flat extending from the front straight portion of the wall 26 and being shaped and contoured to accurately seat the bottom of the impression tray 12.

The interior of the flask also includes a shoulder or shelf 3% integral with and jutting away from the interior surface ofthe wall 26. The shoulder 30 extends along the semi-sircular portion of the wall 26, and is shaped so that it complementally matches the shape of the entire span of the retaining wall (border) 20 of the impression tray 12, when the tray is seated within the flask til, and the elevational contour of said shoulder matches the elevational contour of said border when within the flask. The shoulder 30 also holds the border 29 in spaced relationship from the flask wall 26.

My dental impression molding flask is utilized by placing the impression tray 12 (with a gum, tooth and buccal impression in the impression material 14 carried by the tray) into the molding flask, seating the same therein so that the handle 18 of the tray passes and protrudes through the slot 27 (as shown by direction arrow A of FIG. 1) and so that the body portion 16 seats on the base 2 of the flask. The tray 12 is placed with its impression material facing upward.

As shown in FIGS. 2 through 4, the upper interior face of the base 24 of the flask it including the humped central portion 28 matches the bottom contour of the impression tray and the shoulder 30 running interiorly of and along the upstanding side wall 2i! abuts the entire external surface of the tray border 2%. The flexible resilient characteristic of the material from which the flask is fabricated, and the matched contour of the flask interior and the impression tray automatically effectuate a close, sealing fit over the bearing surfaces between the tray and the flask without the necessity of manipulating any extraneous parts to complete the flask so that the tray can be seated rapidly and accurately in the flask.

When so placed, the impression tray 12 forms the bottom wall of the molding cavity, i.e., the volume into which the molding or casting material will be poured to make a casting. Any suitable dental casting material 32 which flows and then sets up rigidly, e.g. plaster-of- Paris, a gypsum hydrocal or paste, may then be poured into'the molding flask'it). When the casting material 32 hardens, a dental casting 33 is formed which may be readily removed from the flask by virtue of the flexibility and resiliency of the flask.

Referring to FIGS. 4 and 5, it will be seen that the palate area 34a and the tooth and gum surfaces 36a on the impression tray 12 have formed through casting a complementary matched palate area 3412 and complementary tooth and gum'surfaces 36b on the dental casting 33.

Further, the muco-buccal fold 38a in negative form on the impression tray 12 has reproduced a positive fold 38b on the casting 33. The disposition of shoulder 30 protruding inwardly of the wall 26 and against the wall 2% of the impression tray in connection with the interior surface of the flask wall 26 forms an exterior wall or border flange 40 encircling the casting 33 and further defining the fold 38b.

The snug sealing fit of the interior of the flask it? and particularly the shoulder 3t) against the tray 12 and particularly the border 20 prevents the casting material 32 when poured into the molding cavity in liquid state from running around and under the tray or out through the slot 27. This sealed relationship allows usage of a minimum amount of casting material without wastage. This fit also insures that the tray 12 will not slide or move within the flask during the casting process. Such movements would of course form faults or voids in the final dental casting or decrease its density.

Impression materials of the type mentioned, e.g. alginates, are, in common dental practice, immersed in water after an impression of the pa ients mouth has been made therein to keep the impression in good condition over the usual long time delay between the making of the impression by the dentist in his oflice and the making of the dental casting by the dental technician in his laboratory. The use of my molding flask does away with this cumbersome procedure by enabling the dentist to make a casting in his own otfice immediately upon taking the impression from the mouth of the patient. The minimum amount of handling of the impression in such procedure preserves the integrity of the impression in the impression material, reduces the cost of such process and yields immediate results so that the dentist can compare the casting with the patients tooth, gum and buccal surfaces.

Uilization of the impression tray as the bottom wall of the molding cavity has the advantage that the casting material 32 may be slowly and gently poured into the molding cavity without distortion of the tooth, gum and buccal surface impression in the impression material 14; on the tray 12. This may be contrasted with a convential manner of casting such impressions wherein the impression material carried by the tray is pressed downwardly into a container filled with liquid casting, material. In this latter method, the impression material is distorted by the resistance of the dense casting material to displacement. Furthermore because the tray can be correctly seated in the flask without any delay there is no tendency for the impression formed in the impression material to deteriorate.

The dental casting 33 formed by use of my flask needs no trimming or removal of excess hardened casting material before being put to the use intended by the dentist. By closely following the contour of the border of the impression tray 12 by means of the previously described shoulder 39, a neat flnished looking casting is made.

Besides being an accurate replica of the tooth and gum structure of the pa-tients mouth, the muco-buccal fold has also been reproduced by means of the flange 40. The interior face of this flange represents the muco-buccal surface of the month, while the thickness and exterior face of the flange 40 act as a protective barrier in the handling of the casting. Although for most purposes the dental casting 33 is ready for further work by the dentist, trimming or cutting of the flange 42 may be done as. desired.

It thus will be seen that I have provided an apparatus and method of using the same which achieve the several objects of my invention, and which are Well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiment set forth, it is to be understood that all matter herein set forth or shown in the accompmying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. In combination, a dental impression tray carrying impression material and having a curved upstanding wall and a one-piece molding flask of flexible resilient material for forming dental castings from tooth, gum and buccal surface impressions in the impression material carried by the dental impression tray, said flask comprising:

a base shaped to seat the tray,

an upstanding continuous side wall unitarily joined to the base, and

a shoulder integrally jutting from the side wall and shaped to enter into sealed relationship with the wall of the tray.

2. In combination, a one-piece molding flask of flexible resilient material for forming dental castings and a dental impression tray carrying impression material, said tray including a bottom wall and an upstanding border joined to the bottom Wall, said fiask comprising:

a base shaped to seat the tray with its impression material facing upward so that the impression material comprises substantially all of the bottom wall of the molding cavity when the tray is seated within the flask,

an upstanding continuous side wall integral with the base and having an interior plan contour similar to the external plan outline of the tray, and

a shoulder integral with the side wall and protruding internally therefrom, said shoulder abutting substantially the entire exterior surface of the border of the tray and being adapted to enter into sealed relationship therewith whereby said shoulder will prevent the formation of surplus cast material.

3. A one-piece molding flask of flexible resilient material for forming dental castings and for use with an impression tray carrying impression material, said tray including a bottom wall, upstanding border joined to the bottom wall and a handle, said flask comprising:

a base having an upper face which is a complement of the bottom surface of the impression tray and which is shaped to seat the impression tray with its impression material facing upward so that the impression material comprises substantially all of the bottom wall of the molding cavity when the tray is seated within the flask,

an upstanding side wall integral with and joined about the periphery of the base and having a plan interior contour similar to the external plan outline of the tray, said side Wall having an internal height greater than the external height of the tray border and having -a through slot adapted to pass the tray handle, and

a shoulder integral with the side wall and protruding internally therefrom, said shoulder having an interior surface which is the complement of the external surface of the tray border and which is adapted to enter into sealed relationship with substantially the entire exterior tray border surface.

4. In combination, a dental impression tray and a onepiece molding flask of flexible resilient material for forming dental castings from tooth, gum and buccal surface impressions in the impression material carried by the dental impression tray, said tray having a retaining wall having a certain elevational contour, said flask comprising:

a base shaped to seat the tray,

an upstanding continuous side wall unitarily joined to the base, and

a shoulder integrally jutting from the side wall and having an elevational contour matching the elevational contour of the retaining wall of the tray, said shoulder being shaped to enter into sealed relationship with the retaining wall of the tray.

5. A one-piece molding flask of flexible resilient material for forming dental castings and for use with an impression tray carrying impression material, said tray including a bottom wall, an upstanding border joined to the bottom wall and a handle, said flask comprising:

a base shaped to seat the tray with its impression material facing upward so that the impression material comprises substantially all of the bottom wall of the molding cavity when the tray is seated Within the flask,

an upstanding continuous side wall integral with the base and having an interior plan contour similar to the external plan outline of the tray, said side wall having a through slot adapted to snugly pass said handle, and

a shoulder integral with the side Wall and protruding internally therefrom, said shoulder abutting substantially the entire exterior surface of the border of the tray and being adapted to enter into sealed relationship therewith whereby said shoulder will prevent the formation of surplus cast material.

References Cited by the Examiner UNITED STATES PATENTS WILLIAM J. STEEHENSON, Primary Examiner. 

1. IN COMBINATION, A DENTAL IMPRESSION TRAY CARRYING IMPRESSION MATERIAL AND HAVING A CURVED UPSTANDING WALL AND A ONE-PIECE MOLDING FLASK OF FLEXIBLE RESILIENT MATERIAL FOR FORMING DENTAL CASTINGS FROM TOOTH, GUM AND BUCCAL SURFACE IMPRESSIONS IN THE IMPRESSION MATERIAL CARRIED BY THE DENTAL IMPRESSION TRAY, SAID FLASK COMPRISING: A BASE SHAPED TO SEAT THE TRAY, AN UPSTANDING CONTINUOUS SIDE WALL UNITARILY JOINED TO THE BASE, AND A SHOULDER INTEGRALLY JUTTING FROM THE SIDE WALL AND SHAPED TO ENTER INTO SEALED RELATIONSHIP WITH THE WALL OF THE TRAY. 